Ruger SR-556VT Review
Part 3 - External & Operational Features
June 1, 2013

In this part of my Ruger SR-556VT Review, I try to cover all the external and operational features of the SR-556VT rifle.  Back in 2011, I also reviewed the SR-556C and you can look at that review by going to this link to see the similar features on the SR-556C.

 

These next photos give you some overall isometric views of the Ruger SR-556VT rifle.  Note that the bipod shown does not come with the rifle.  Overall the SR-556VT has a sleek look with its black polymer and black anodized aluminum components and is accented with the stainless barrel and chrome plated bolt carrier.  Although I don't think it was Ruger's original intent to make a "compliant" rifle when they started out planning for this varmint/target platform,  this rifle's configuration represents one that doesn't have controversial features such as a flash hider, collapsible stock and standard capacity (30 rounds) magazines.  I feel Ruger's real goal was to produce a true varmint/target platform based on their SR-556 rifle platform. In reality, installing a collapsible stock only takes about 15 minutes and the rifle will accept any standard AR-15 style magazine. 

Figure 1

Figure 2

Figure 3

Figure 4

These next four photos were included in the last part of this review and are also included here because they show the primary views of the SR-556VT rifle.  The SR-556VT measured 38.50" in length which is slightly longer than the 38.25" stated in the specifications.  The width of the rifle at it's widest points, which are across the extended charging handle and forward assist, measured about 3.25".  The specifications stated 2.50" and I feel like the specs don't take into account the extended charging handle.

Figure 5

The height of the rifle from the top of the upper receiver to the bottom of the grip measured 7.18" which was also less than the specification height of 7.75".  I think the specs represent a rifle with a slightly different grip and with sights installed.

Figure 6

Figure 7

Figure 8

The main feature that sets this model of the SR-556 apart from the others is the 20" cold hammer-forged 410 stainless steel barrel.  Hammer forging is a process where a drilled and reamed barrel blank has its rifled bore and chamber formed by swaging. During production of the barrel, the internal profile is formed by a series of opposing power hammers which concentrically “crush” the drilled blank around a precision-ground and hardened mandrel. This process yields an extremely uniform bore with a tough, consistent surface finish on the inside of the barrel. The forging process also work hardens the barrel steel resulting in a very durable and much longer lasting barrel. The stainless steel characteristics give the barrel good corrosion resistance and also help resist bore erosion.  The photo below shows that you can see the stainless steel barrel through the slots in the handguard.

Figure 9

The barrel measured a constant diameter of 0.700" on the exposed areas forward of the gas block.  It steps up to 0.750" at the gas block and then appears to change to about (couldn't measure exactly) 0.85" from the rear of the gas block to a point approximately 4" forward of the upper receiver where it tapers up to a diameter to accept a barrel extension.

Figure 10

The end of the barrel has a target crown as shown below.  The crown's profile appearance and chamfers on the inside and outside of the barrel appear to be even in shape and concentric.

Figure 11

The barrel is chambered in 5.56 NATO and has a 6 groove 1:8 Right Hand twist.  This information is stamped on the top of the barrel as shown below.  This 5.56 NATO cambering allows for use of the slightly lower pressure .223 Remington cartridge.  The 1:8 twist is able to stabilize bullet lengths up to 80 grains in weight.

Figure 12

The bottom of the barrel is stamped with the warning statement "BEFORE USING READ INSTRUCTION MANUAL" and manufacturer's name and place of manufacture "RUGER, NEWPORT, NH U.S.A.".

Figure 13

Figure 14

The SR-556 rifles utilize a two-stage piston driven gas operating system.  This piston system is apparent by the presence of the pressure selector which is located on the front of the gas block.  Another feature worth noting in the photo below is that the handguard is supported on the forward end by the gas block, which means that the barrel is not free floated.  Since the SR-556 is a piston rifle, I feel a truly floated barrel cannot be achieved due to the interaction of the transfer rod and spring forces which are part of the piston system.  Perhaps this handguard to gas block contact will allow the stiffness of the handguard to act in conjunction with the barrel so that the portion of the barrel up to the gas block has a much greater stiffness than just the barrel alone.  In the end, as long as the rifle is accurate, these details may not be of importance.

Figure 15

The gas block measures 3.175" in length with the top rail being the longest part of the gas block. The top front of the block has an arrow made from 5 dots identifying the gas port setting (i.e. "2" shown in the photo below).  The gas block is made from steel and is Manganese Phosphate coated (Parkerized). It is this coating that gives this part its dark-gray color.

Figure 16

You can see in the photo below the head of the regulator pin and the regulator detent clip.  This clip indexes in the holes around the regulator to prevent the regulator from rotating during use.  The gas block also maintains the same height as the upper handguard rail and upper receiver rail which allows for mounting a common height forward sight.

Figure 17

On the bottom of the gas block is a hole to allow for staking the solid rear gas block pin to prevent it from working loose over time.  A forward sling swivel stud is attached to the front lower portion handguard.

Figure 18

The regulator pin has a dimple on the end to allow you to push the pin to the left while using the tip of a bullet.

Figure 19

This next photo shows the gas regulator, detent clip and piston removed.  Instructions for removal of the gas piston are included in Part 4 of this review.

Figure 20

The exterior of the regulator (black knob) is marked with 0, 1, 2, 3, and an "arrow". The 0 setting causes the rifle to function in a single shot mode. The 1, 2 and 3 represent gas port openings from smallest to largest. The "arrow" is the position to use for removal of the regulator.  The gas regulator was also marked with "VT".  This marking was not on my SR-556C, so I tried to measure some of the port (hole) openings for comparison.  Clearly the "VT" gas regulator is not the same as my SR-556C.  The smallest hole diameter on the "VT" is slightly larger than the smallest on the SR-556C and the largest hole diameter on the "VT" is smaller than the largest on the SR-556C.  It seems that Ruger has tuned the "VT" regulator around the mid range of the SR-556C regulator.  At the time of this review, Ruger doesn't show any SR-556VT specific parts in their Owner's Manual, but I expect they will eventually update the manual and identify this as a different part from their other rifles.

Figure 21                 Figure 22                 Figure 23                 Figure 24                 Figure 25
       

The two-stage gas regulator works by gasses passing through a hole in the regulator and then applying pressure against the smaller diameter of the piston that is inside the regulator.

Figure 26

Once the piston is pushed out of the regulator, gas pressure can also act on the larger diameter of the piston.

Figure 27

Ruger chose to use the same handguard as their SR-556E rifle which has a simple slim profile and includes an upper integral Picatinny rail.  This handguard is made from aluminum and has a black anodized finish with the Ruger logo and "RUGER" stenciled on the right side near the receiver.

Figure 28

The SR-556VT comes with two 3" sections of Picatinny rail which can be incorporated at various positions along the handguard at the 3, 6 & 9 o'clock locations.  The rifle also comes with three 5.75" rail covers.  The photo below shows the rails and covers installed.

Figure 29

The top slots in the Picatinny rail on the handguard are marked in a white lettering with the typical markings (i.e. T16, T18, etc.).  The handguard measured 1.60" in width.

Figure 29

The height of the handguard measured 2.22" to the top of the rail.  The overall length of the handguard was ~10.94".  Each side and the bottom of the handguard is drilled and tapped with holes to allow mounting the short 3" rail sections at up to 4 different locations along the rail.  You can also use these holes to mount the rail covers that come with the rifle.

Figure 30

At the rear bottom of the handguard, you can see the two handguard mounting screws which tighten the handguard against the barrel nut.  After trying to look down the handguard and studying the Owner's Manual, it appears the barrel nut is a custom nut designed to support this handguard.

Figure 31

Since I didn't remove the handguard because the Owner's Manual states that it "must be factory fitted", I had to speculate based on studying the external geometry and manual that the rear bushing that goes between the upper receiver rail and handguard rail is also used to help pin the two parts together.  The two roll pins appear to serve the pinning purpose.

Figure 32

The rifle weighed in at 8.39 pounds with an empty magazine and no extra features installed.  The heavier barrel profile and additional barrel length added about one pound of weight compared to my SR-556C.  Because of the added weight to the front of the rifle, this weight gives the rifle a heavy front end feel.  Since the SR-556VT is intended for varmint or target shooting, the reduction in point-ability should not hurt and the added mass may help to absorb recoil.

Figure 33

With the two rails and three rail covers installed, the rifle weighed in at 8.64 pounds.

Figure 34

As I mentioned earlier in the review, the rifle I received had already seen some action which is evident by the scuff marks on the top of the Picatinny rail on the upper receiver.  The scuff marks are clearly visible in the photo below and a new rifle will not look like this.  The photos below also give you a good look at the extended charging handle which helps with traditional style scopes installed on an AR style rifle.

Figure 35

Figure 36

Two of the key components in any AR styled rifle are the upper and lower receivers.  Both receivers are machined from forged 7075-T6 aluminum and are Type III Hardcoat Anodized.  In general, these materials have become the standard for these components on quality rifles.  The upper forging appears to be made by Anchor-Harvey based on the forging mark which looks like an "A" with a split in the middle.  The upper and lower receiver configurations appear to be standard with the upper including a case deflector, forward assist and ejection port cover.  The lower is configured with a right hand only safety.

The SR-556VT comes with a Magpul MOE^® Grip.  According to the Magpul website, the features of this grip are as follows.

• The MOE Grip provides Magpul quality, feel, and durability in an economical, drop-in upgrade for the standard AR15/M16/M4 pistol grip.
• The ergonomic, hand filling design combines aggressive texturing with storage core capability.
• With a similar shape to a 'medium' sized MIAD, the one-piece reinforced polymer construction provides simplicity and a reduced cost while still maintaining the durability needed to withstand operational environments.
• The MOE Grip accepts optional storage cores for gear stowage and includes a basic grip cap.

This grip gives a Length of Trigger Pull (LOTP) of 2.57" which is the distance from where the web of your hand (between your thumb and index finger) presses and the front face of the trigger.  As a comparison, the Hogue grip on the SR-556C has a LOTP of 2.35".  I agree with Ruger that the increased LOTP does help with trigger finger placement.

Figure 37

The photo below shows the grip cap removed and you can see the interior area which accepts various Magpul Storage Cores.

Figure 38

The lower receiver will accept any standard AR-15 style magazines.

Figure 39

The lower receiver is marked with the Ruger logo, Ruger name, manufacturing location, serial number, model "SR-556", and the safe/fire markings for the safety.  The controls on the left side are the standard safety and bolt release.

Figure 40

To check the fit of the upper and lower receivers, I applied pressure so that all the gap was on one side of the receivers and then used a feeler gauge to determine the gap thickness.  In this case, I was able to get a 0.004" feeler gauge between the two receivers throughout the entire length.  This gap is typical of many AR style rifles and is seen as a slight rattle between the receivers.  Based on some of the other ARs I have measured, this 0.004" gap is one of the smallest.

Figure 41

The trigger pull measured 3.7 pounds based on an average of 10 pulls using a Lyman Digital Trigger Pull Scale.  The two stage trigger had a light initial take-up  on the first stage then a very slight bit of creep before it broke and had no detectable overtravel on the second stage.  Overall I think most people would be pleased with the trigger pull on this rifle.

Figure 42

In this next series of photos, I show the ejection port cover closed, then open with the bolt carrier forward, and last open with the bolt carrier rearward (open).

Figure 43

Other than the Ruger logo on the bolt carrier, there was nothing that seemed to stand out when looking at the ejection port area.

Figure 44

Figure 45

These next several photos give you some isometric views of the upper and lower receivers.

Figure 46

Figure 47                                                        Figure 48
  

Figure 49                                                         Figure 50 
  

The buttstock on the SR-556VT rifle is a standard A2 style fixed length buttstock.  I compared this stock against one from my Colt Sporter II that was manufactured back in the 80's and didn't see any significant difference.

Figure 51

The stock is made from some type of black polymer (synthetic) material and has a fixed length of pull of 13.68".  This measurement was about 1/16" less than the 13.75" stated in the specs and the difference is probably due to variations in measurement locations on the butt plate.

Figure 52

The stock comes with a sling loop that is held in place by the lower butt plate screw.

Figure 53

The stock includes a door on the butt plate to access a storage compartment for a cleaning kit, small parts, or other accessories.  The butt plate is made from a hard polymer material and provides no recoil absorbing characteristics.

Figure 54                                                            Figure 55             
  

The SR-556VT comes with three 5-round magazines made by C Products Defense.  The features of this magazines are as follows:

• Material: 400 Series Stainless Steel
• Finish: Matte Black
• Follower: Orange Plastic Anti-Tilt
• Spring: Chrome Silicon Wire

Figure 56
      

Figure 57                                          Figure 58                                                 Figure 59 
     

Figure 60

Figure 61

These next two photos show the magazine loaded with Hornady 55gr A-Max and 75gr BTHP Match ammunition.

Figure 62

Figure 63

 

Thoughts

I was pleased with the trigger pull on the rifle and like the handguard configuration.  I'm shifting to a philosophy that less is more and four full quad rails would be of no benefit on this rifle.  The A2 stock is very simple and functional, but I think adding a stock like the Magpul MOE Rifle Stock would have been a nice touch to go along with the Magpul grip.

For more detailed photos and commentary, make sure you check out the other parts of this review and feel free to leave comments on my Reader's Comments page.  The following links are provided to help you see other parts of this review. 

• Ruger SR-556VT Review: Part 1 - Introduction, Specifications and Summary
• Ruger SR-556VT Review: Part 2 - What's in the Box
• Ruger SR-556VT Review: Part 3 - External and Operational Features (this page)
• Ruger SR-556VT Review: Part 4 - Disassembly
• Ruger SR-556VT Review: Part 5 - Internal Features
• Ruger SR-556VT Review: Part 6 - Range Test

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